In which TV series is Fox Mulder a main character?

Who played Topanga Lawrence in 'Boy Meets World'? Who played Mr. Feeny in 'Boy Meets World'? In which TV series is Mr. Feeny a main character? Who played Fox Mulder in 'The X-Files'? Who played Dana Scully in 'The X-Files'? In which TV series is Dana Scully a main character? Who played Frasier Crane in 'Frasier'? Who played Niles Crane in 'Frasier'?